The Liquid Crystal Display (LCD) possesses advantages of thin body, power saving and no radiation to be widely used in many application scope. Such as LCD TV, mobile phone, personal digital assistant (PDA), digital camera, notebook, laptop, and dominates the flat panel display field.
Most of the liquid crystal displays on the present market are back light type liquid crystal displays, which comprise a shell, a liquid crystal display panel located in the shell and a backlight module located in the shell. The liquid crystal display panel is a major component of the liquid crystal display. However, the liquid crystal display panel itself does not emit light and needs the back light module to provide light source for normally showing images.
Generally, the liquid crystal display panel comprises a Color Filter (CF), a Thin Film Transistor Array Substrate (TFT Array Substrate) and a Liquid Crystal Layer positioned between the two substrates. Meanwhile, pixel electrodes, common electrodes are provided respectively at relative inner sides of the two substrates. The light of back light module is reflected to generate images by applying voltages to control the liquid crystal molecules to be changed directions.
The liquid crystal displays have kinds of display types, including Twisted Nematic (TN) type, Electrically Controlled Birefringence (ECB) type, Vertical Alignment (VA) type and et cetera. The VA type is a common display type with benefits of high contrast, wide view angle and rubbing alignment free. However, because the VA type utilizes vertical twist liquid crystals and the birefraction difference of the liquid crystal molecules is larger, the issue of the color shift under large view angle is more serious.
Reducing the color shift is the requirement for the development of the VA type liquid crystal displays. At present, the mainstream method of solving the color shift of the VA type liquid crystal displays is multi domain, such as a pixel design of 8 domain display. The twisted angles of the liquid crystal molecules of the 4 domains in the main area (main) and the 4 domains in the sub area (sub) in the same sub pixel are different to improve the color shift. The color shift improvement skill mainly comprises capacitor coupling (CC) technology, charge sharing (CS) technology, common electrode voltage (Vcom) modulation technology, 2D1G/2G1D technology. However, lots of color shift improvement technologies makes the liquid crystal twist polarities of the main area and the sub area in one sub pixel are the same, and cannot achieve that the main area and sub area in one sub pixel shows opposite polarities in one frame of an image, which results in that the flicker of the liquid crystal display panel is more obvious to reduce the display quality. Although 2D1G color shift improvement technology can solve the issue of panel flicker, it requires to double the amount of the data signal lines, and the amount of the Chip on Films (COF) is also required to be doubled, too. The panel cost will increase.
FIG. 1 shows an overall structure diagram of a pixel circuit for improving the color shift issue of a VA type liquid crystal display, and FIG. 2 is a specific circuit diagram in accordance with FIG. 1. With combination of FIG. 1 and FIG. 2, a plurality of sub pixels arranged in array, and each sub pixel is divided into a main area Main and a sub area Sub; one scan line is provided in accordance with to sub pixels of each row, and one data signal line, a voltage dividing unit 100 and a wiring are provided in accordance with sub pixels of each column. M, N are set to be positive integers, and a Mth scan line G(M) is electrically coupled to the main area Main and the sub area Sub of the sub pixels of Mth row at the same time and provides a scan signal to the same; a Nth data line D(N) is electrically coupled to the main area Main of the sub pixels of Nth column and provides a main data signal voltage to the same, and the Nth data line D(N) is electrically coupled to the common electrode Com via the voltage dividing unit 100, and the corresponding Nth routing L(N) is led out from the voltage dividing unit 100, and is electrically coupled to the sub areas Sub of the sub pixels of the N column and provides a sub data signal voltage which is different from the main data signal voltage to the same.
Specifically, the voltage dividing unit 100 comprises a first capacitor C1 and a second capacitor C2 coupled in series, and one end of the first capacitor C1 is electrically coupled to the data signal line, and the other end is electrically coupled to one end of the second capacitor C2, and the other end of the second capacitor C2 is electrically coupled to a common electrode line Com. The Nth routing L(N) is led out between the first capacitor C1 and the second capacitor C2, and with voltage dividing function of the first capacitor C1 and the second capacitor C2, the sub data signal voltage is closer to the common electrode voltage than the main data signal voltage, i.e. the voltage difference of the sub data signal voltage and the common electrode voltage is definitely smaller than the voltage difference of the main data signal voltage and the common electrode voltage. With applying different voltages to the main area Main and the sub area Sub in one pixel, the objective of improving the color shift can be achieved.
The aforesaid pixel circuit according to prior art can solve the color shift issue of VA type liquid crystal display but the polarities of the main data signal voltage and the sub data signal voltage provided by the Nth data line D(N) corresponding to the sub pixels of Nth column and the corresponding Nth routing L(N) are the same. Therefore, in the image of the same frame, the polarities of the voltages applied to the main area Main and the sub area Sub in one pixel are the same, which remains to make that the flicker of the liquid crystal display panel is more obvious to reduce the display quality.